Logan, John David. <br/><br/>
Invariant variational principles   
by John David Logan 
 - New York  Academic Press  1977 
 - xv, 172p. 
 - Mathematics in Science and Engineering  V.138 .
<br/><br/><label>ISBN: </label>0124547508 
<br/><br/><label>Dewey Class. No.: </label>515.64  / N771